Rosario is the former estate of Seattle mayor and shipbuilder Robert Moran and is located on Orcas Island, Washington in the San Juan archipelago.

Portions of the estate became part of Moran State Park in the early 1920s and the site has been of use as the Rosario Resort and Spa since 1960.

Due to poor health, Robert Moran, a former Seattle Mayor and shipbuilder, moved to Orcas Island and between 1906 and 1909 built his estate.

[2][6] Constructed in an Arts & Crafts style, the 5-story resort was named after the Rosario Strait and contains a music room that features a 1913 two-story 34-rank German-style Aeolian organ consisting of over 1,900 pipes and a 1900 Steinway grand piano.

[4] The Rosario mansion features a museum honoring Robert Moran, complete with original furnishings.